feat: Implement ES256 for JWT verification (#340)
feat: Implement EC256 for JWT verification
diff --git a/google/auth/crypt/__init__.py b/google/auth/crypt/__init__.py
index 39929fa..15ac950 100644
--- a/google/auth/crypt/__init__.py
+++ b/google/auth/crypt/__init__.py
@@ -31,6 +31,10 @@
private_key = open('private_key.pem').read()
signer = crypt.RSASigner.from_string(private_key)
signature = signer.sign(message)
+
+The code above also works for :class:`ES256Signer` and :class:`ES256Verifier`.
+Note that these two classes are only available if your `cryptography` dependency
+version is at least 1.4.0.
"""
import six
@@ -38,8 +42,23 @@
from google.auth.crypt import base
from google.auth.crypt import rsa
+try:
+ from google.auth.crypt import es256
+except ImportError: # pragma: NO COVER
+ es256 = None
-__all__ = ["RSASigner", "RSAVerifier", "Signer", "Verifier"]
+if es256 is not None: # pragma: NO COVER
+ __all__ = [
+ "ES256Signer",
+ "ES256Verifier",
+ "RSASigner",
+ "RSAVerifier",
+ "Signer",
+ "Verifier",
+ ]
+else: # pragma: NO COVER
+ __all__ = ["RSASigner", "RSAVerifier", "Signer", "Verifier"]
+
# Aliases to maintain the v1.0.0 interface, as the crypt module was split
# into submodules.
@@ -48,9 +67,13 @@
RSASigner = rsa.RSASigner
RSAVerifier = rsa.RSAVerifier
+if es256 is not None: # pragma: NO COVER
+ ES256Signer = es256.ES256Signer
+ ES256Verifier = es256.ES256Verifier
-def verify_signature(message, signature, certs):
- """Verify an RSA cryptographic signature.
+
+def verify_signature(message, signature, certs, verifier_cls=rsa.RSAVerifier):
+ """Verify an RSA or ECDSA cryptographic signature.
Checks that the provided ``signature`` was generated from ``bytes`` using
the private key associated with the ``cert``.
@@ -60,6 +83,9 @@
signature (Union[str, bytes]): The cryptographic signature to check.
certs (Union[Sequence, str, bytes]): The certificate or certificates
to use to check the signature.
+ verifier_cls (Optional[~google.auth.crypt.base.Signer]): Which verifier
+ class to use for verification. This can be used to select different
+ algorithms, such as RSA or ECDSA. Default value is :class:`RSAVerifier`.
Returns:
bool: True if the signature is valid, otherwise False.
@@ -68,7 +94,7 @@
certs = [certs]
for cert in certs:
- verifier = rsa.RSAVerifier.from_string(cert)
+ verifier = verifier_cls.from_string(cert)
if verifier.verify(message, signature):
return True
return False
diff --git a/google/auth/crypt/es256.py b/google/auth/crypt/es256.py
new file mode 100644
index 0000000..5bfd57f
--- /dev/null
+++ b/google/auth/crypt/es256.py
@@ -0,0 +1,145 @@
+# Copyright 2017 Google Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""ECDSA (ES256) verifier and signer that use the ``cryptography`` library.
+"""
+
+import cryptography.exceptions
+from cryptography.hazmat import backends
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives import serialization
+from cryptography.hazmat.primitives.asymmetric import ec
+from cryptography.hazmat.primitives.asymmetric import padding
+import cryptography.x509
+import pkg_resources
+
+from google.auth import _helpers
+from google.auth.crypt import base
+
+_IMPORT_ERROR_MSG = (
+ "cryptography>=1.4.0 is required to use cryptography-based ECDSA " "algorithms"
+)
+
+try: # pragma: NO COVER
+ release = pkg_resources.get_distribution("cryptography").parsed_version
+ if release < pkg_resources.parse_version("1.4.0"):
+ raise ImportError(_IMPORT_ERROR_MSG)
+except pkg_resources.DistributionNotFound: # pragma: NO COVER
+ raise ImportError(_IMPORT_ERROR_MSG)
+
+
+_CERTIFICATE_MARKER = b"-----BEGIN CERTIFICATE-----"
+_BACKEND = backends.default_backend()
+_PADDING = padding.PKCS1v15()
+
+
+class ES256Verifier(base.Verifier):
+ """Verifies ECDSA cryptographic signatures using public keys.
+
+ Args:
+ public_key (
+ cryptography.hazmat.primitives.asymmetric.ec.ECDSAPublicKey):
+ The public key used to verify signatures.
+ """
+
+ def __init__(self, public_key):
+ self._pubkey = public_key
+
+ @_helpers.copy_docstring(base.Verifier)
+ def verify(self, message, signature):
+ message = _helpers.to_bytes(message)
+ try:
+ self._pubkey.verify(signature, message, ec.ECDSA(hashes.SHA256()))
+ return True
+ except (ValueError, cryptography.exceptions.InvalidSignature):
+ return False
+
+ @classmethod
+ def from_string(cls, public_key):
+ """Construct an Verifier instance from a public key or public
+ certificate string.
+
+ Args:
+ public_key (Union[str, bytes]): The public key in PEM format or the
+ x509 public key certificate.
+
+ Returns:
+ Verifier: The constructed verifier.
+
+ Raises:
+ ValueError: If the public key can't be parsed.
+ """
+ public_key_data = _helpers.to_bytes(public_key)
+
+ if _CERTIFICATE_MARKER in public_key_data:
+ cert = cryptography.x509.load_pem_x509_certificate(
+ public_key_data, _BACKEND
+ )
+ pubkey = cert.public_key()
+
+ else:
+ pubkey = serialization.load_pem_public_key(public_key_data, _BACKEND)
+
+ return cls(pubkey)
+
+
+class ES256Signer(base.Signer, base.FromServiceAccountMixin):
+ """Signs messages with an ECDSA private key.
+
+ Args:
+ private_key (
+ cryptography.hazmat.primitives.asymmetric.ec.ECDSAPrivateKey):
+ The private key to sign with.
+ key_id (str): Optional key ID used to identify this private key. This
+ can be useful to associate the private key with its associated
+ public key or certificate.
+ """
+
+ def __init__(self, private_key, key_id=None):
+ self._key = private_key
+ self._key_id = key_id
+
+ @property
+ @_helpers.copy_docstring(base.Signer)
+ def key_id(self):
+ return self._key_id
+
+ @_helpers.copy_docstring(base.Signer)
+ def sign(self, message):
+ message = _helpers.to_bytes(message)
+ return self._key.sign(message, ec.ECDSA(hashes.SHA256()))
+
+ @classmethod
+ def from_string(cls, key, key_id=None):
+ """Construct a RSASigner from a private key in PEM format.
+
+ Args:
+ key (Union[bytes, str]): Private key in PEM format.
+ key_id (str): An optional key id used to identify the private key.
+
+ Returns:
+ google.auth.crypt._cryptography_rsa.RSASigner: The
+ constructed signer.
+
+ Raises:
+ ValueError: If ``key`` is not ``bytes`` or ``str`` (unicode).
+ UnicodeDecodeError: If ``key`` is ``bytes`` but cannot be decoded
+ into a UTF-8 ``str``.
+ ValueError: If ``cryptography`` "Could not deserialize key data."
+ """
+ key = _helpers.to_bytes(key)
+ private_key = serialization.load_pem_private_key(
+ key, password=None, backend=_BACKEND
+ )
+ return cls(private_key, key_id=key_id)